The invention relates to an apparatus for counterbalancing the weight of movable machine components of a machine tool.
In the field of machine tools (he weight of the vertically movable machine parts is often counterbalanced by counterweights to decrease the driving power during lifting operations as well as to increase the acceleration, said counterweights being connected to the movable machine parts such as, for example, milling units, consoles or transverse beams via roller chains or ropes. Particularly in machine tools of compact construction, however, there is no space for such counterweights and the additionally required guidances.
Therefore, a hydraulic or hydro-pneumatic weight counterbalance is also used already in which the weight of a vertically shiftable machine part is compensated by one or more pressure cylinders. However, corresponding means for the pressure means supply and control members for adjusting and maintaining the pressure in the pressure cylinders are required in this type of weight compensation.
It is the object of the invention to provide an apparatus of the type mentioned at the beginning which is simple and compact in design and will also enable weight compensation without complex pressure means supplies and control means.
According to the invention said object is solved in that the apparatus comprises one or more helical springs one end of which is connected to a stationary component and the other end of which is connected to the movable machine part to generate a counter-force counteracting the weight force of the movable machine part.
With the apparatus according to the invention particularly the weight force of vertically or obliquely movable machine parts may be totally or partially counterbalanced with simple means. In this way the driving power required for lifting the machine parts can be reduced. The feeding drive is less strained even when larger masses are lifted, and a greater acceleration is obtainable.
Efficacious embodiments and advantageous forms of the invention are indicated in the sub-claims.
Thus, the apparatus comprises a plurality of parallel connected helical springs in a particularly efficacious embodiment, said helical springs being disposed between the machine part to be moved and a stationary component. With a plurality of helical springs the spring characteristic may be optimally adjusted to the prevailing requirements. In addition, safety is provided for the case that a break or the like occurs in one of the helical springs.
In an embodiment sealed towards the outside to a large extent the inner end of the helical springs is attached to an axis and the other to a housing concentric with respect to the axis. The axis may be arranged so as to be stationary, and the housing may be formed so as to be turnable. However, the housing may as well be designed so as to be stationary, and the axis may be formed so as to be rotatable.
In an embodiment with a fixed axis and a movable housing the latter is advantageously connected to the machine part to be moved via a gear belt capable of enduring great loads which will be wound up on the efficaciously drum shaped central part of the housing when the machine part is lifted. However, other pulling elements may also be used for connecting the housing with the shiftable machine part.
According to another efficacious embodiment the helical springs disposed adjacent to each other are separated from each other by spacer disks. In this way an undesired friction between the individual springs may be prevented.
For biasing the helical springs a corresponding adjustment flange may be provided on the axis which flange can be turned via radial bores and fixed on an angular console or another stationary machine part in a desired angular position via front side fixing screws or the like.